Method of determining very small capacitances

US6583632B2 · kind B2 · utility

Assignee

• Micronas GmbH · DE

Inventors

• Paul-Werner von Basse · Wolfratshausen, DE
• Josef Willer · Riemerling, DE

Key dates

• Filing date: Jan 23, 2001
• Grant date: Jun 24, 2003
• Expiry date: Jan 23, 2021

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R27/2605
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A grid of capacitor surfaces is connected to read lines and control lines. The read lines are connected alternately to the output of a feedback operational amplifier and to a collecting capacitor. The capacitances to be measured are charged repeatedly and the charges are collected on the collecting capacitors. Between the charging operations, the potential on the read lines is kept constant through the use of the low-resistance output of the operational amplifier. The use of this method in the case of a fingerprint sensor makes it possible to evaluate all the read lines together.